<sarcasm font> you're absolutely right, we should have left the entire marvel and DC universes completely self-contained and never made internal crossovers like the Avengers or Teen Titans. <end sarcasm font>

If you don't like something just ignore it and move on with your life.

They do it just because crossovers are always cool in one way or another.
As a Whovian (among other fandoms with which I identify), I would think Wolverine in the Doctor Who universe would be really awesome.

Now that I think about it, it's because The Doctor just kind of shows up anywhere and anywhen he cares to, which almost no other protagonist in any other fandom can do.

Maybe someone could make a sort of SotC mod that replaces some of the colossi with various kinds of Titans, but keep the gameplay the same.
Then allow a sort of replay where you can try again but as a Titan.